JP6797166B2 - Plating bath and method - Google Patents

Description

The present invention generally relates to the field of electrolytic metal plating. In particular, the present invention relates to the field of electrolytic copper plating.

The method of electroplating an article with a metal coating generally involves passing an electric current between two electrodes in the plating solution, one of which is the article to be plated. A typical copper acid plating solution improves dissolved copper (usually copper sulphate), an amount of acid electrolyte sufficient to provide conductivity to the bath, such as sulfuric acid, as well as plating uniformity and quality of metal deposits. Contains labeled additives to cause. Examples of such additives include accelerators, smoothing agents and inhibitors.

Electrolytic copper plating solutions are used in various industrial applications such as decorative and anti-corrosion coatings, and in the electronics industry, especially for the production of printed circuit boards and semiconductors. For circuit board manufacturing, copper is electroplated on selected parts of the surface of the printed circuit board, in the blinds, and on the walls of through holes that penetrate between the surfaces of the circuit board base material. The walls of the through holes are first made conductive, for example by electroless metal deposition, before copper is electroplated onto the walls of the through holes. The plated through holes provide a conductive path from one surface of the plate to the other. For semiconductor manufacturing, copper is electroplated on the surface of a wafer that contains various features, such as vias, grooves, or a combination thereof. Vias and grooves are metallized to provide conductivity between the various layers of the semiconductor device.

The use of accelerators and / or smoothing agents in electroplating baths to achieve uniform metal deposits on the surface of the substrate in certain areas of plating, such as in electroplating of printed circuit boards (PCBs). It is well known that it can be important. Plating a substrate with an irregular shape can pose special difficulties. Voltage drop fluctuations during electroplating will typically be along an irregular surface, which can result in non-uniform metal deposits. Plating irregularities is exacerbated when voltage drop fluctuations are relatively excessive, i.e., where surface irregularities are substantial. As a result, thick metal deposits called overplating are observed on such surface irregularities. As a result, a metal layer of substantially uniform thickness is often a difficult process in the manufacture of electronic devices. Smoothing agents are often used in copper plating baths to provide a substantially uniform or smooth copper layer in electronic devices.

The trend of portability combined with the increased functionality of electronic devices has driven the miniaturization of PCBs. Traditional multilayer PCBs with through-hole internal connection vias are not always a practical solution. Other attempts have been developed for high-density internal connections, such as sequential build-up techniques that utilize blinds. One of the objectives of the process using the blinds is to maximize the via filling while minimizing the thickness variation of the copper deposits over the surface of the substrate. This is especially difficult if the PCB contains both through holes and blinds.

Generally, the smoothing agent used in the copper plating bath provides good smoothing of deposits over the surface of the substrate, but tends to worsen the uniform electrodeposition of the electroplating bath. Uniform electrodeposition is defined as the ratio of the thickness of the copper deposit in the center of the hole to the thickness of the copper deposit on its surface. New PCBs are being manufactured, including both through-holes and blinds. Current bath additives, especially current smoothing agents, do not provide smooth copper deposits on the surface of the substrate and do not effectively fill through holes and / or effectively fill blinds. ..

For example, US Pat. No. 7,374,652 (Hayashi et al.) From a copper plating bath containing a smoothing agent that is the reaction product of a particular unsubstituted heterocyclic amine to a polyepoxide compound containing an alkyleneoxy bond. Disclosed is a method of producing smooth copper deposits by electroplating copper. Even with such smoothing agents, smooth, nodule-free copper deposits on the surface of the substrate, and filled through-holes or blinds are not always produced.

U.S. Pat. No. 7,374,652

In the art, for the production of PCBs that provide smooth copper deposits without significantly affecting the uniform electrodeposition of the bath, i.e., while the bath effectively fills the blinds and through holes. There is a need for smoothing agents for use in the copper electroplating baths used.

（式中、Ｙ^１およびＹ^２は独立してＨおよび（Ｃ_１−Ｃ_４）アルキルから選択され；ＺはＡｒ、Ｒ^１２ＯＡｒＯＲ^１２、（Ｒ^１３Ｏ）_ａＡｒ（ＯＲ^１３）_ａ、Ｃｙ、Ｒ^１２ＣｙＲ^１２もしくは（Ｒ^１３Ｏ）_ａＣｙ（ＯＲ^１３）_ａ；ｒ＝１〜４；Ａｒ＝（Ｃ_６−Ｃ_１８）アリール；Ｃｙ＝（Ｃ_５−Ｃ_１２）シクロアルキル；各Ｒ^１２は（Ｃ_１−Ｃ_８）アルキルを表し；各Ｒ^１３は（Ｃ_２−Ｃ_６）アルキレンオキシを表し；各ａ＝１〜１０；並びに、Ａは（Ｃ_５−Ｃ_１２）シクロアルキルを表す）
の１種以上のエポキシド含有化合物との反応生成物を提供する。
本発明は、銅イオン源、電解質および平滑化剤を含む銅電気めっき浴であって、平滑化剤が１種以上の窒素含有化合物と式（Ｉ）もしくは（ＩＩ）：

（式中、Ｙ^１およびＹ^２は独立してＨおよび（Ｃ_１−Ｃ_４）アルキルから選択され；ＺはＡｒ、Ｒ^１２ＯＡｒＯＲ^１２、（Ｒ^１３Ｏ）_ａＡｒ（ＯＲ^１３）_ａ、Ｃｙ、Ｒ^１２ＣｙＲ^１２もしくは（Ｒ^１３Ｏ）_ａＣｙ（ＯＲ^１３）_ａ；ｒ＝１〜４；Ａｒ＝（Ｃ_６−Ｃ_１８）アリール；Ｃｙ＝（Ｃ_５−Ｃ_１２）シクロアルキル；各Ｒ^１２は（Ｃ_１−Ｃ_８）アルキルを表し；各Ｒ^１３は（Ｃ_２−Ｃ_６）アルキレンオキシを表し；各ａ＝１〜１０；並びに、Ａは（Ｃ_５−Ｃ_１２）シクロアルキルを表す）
の１種以上のエポキシド含有化合物との反応生成物である、銅電気めっき浴も提供する。
本発明は、銅イオン源、電解質および平滑化剤を含む銅電気めっき浴であって、平滑化剤が１種以上の窒素含有化合物と式（Ｉ）もしくは（ＩＩ）：

（式中、Ｙ^１およびＹ^２は独立してＨおよび（Ｃ_１−Ｃ_４）アルキルから選択され；ＺはＡｒ、Ｒ^１２ＯＡｒＯＲ^１２、（Ｒ^１３Ｏ）_ａＡｒ（ＯＲ^１３）_ａ、Ｃｙ、Ｒ^１２ＣｙＲ^１２もしくは（Ｒ^１３Ｏ）_ａＣｙ（ＯＲ^１３）_ａ；ｒ＝１〜４；Ａｒ＝（Ｃ_６−Ｃ_１８）アリール；Ｃｙ＝（Ｃ_５−Ｃ_１２）シクロアルキル；各Ｒ^１２は（Ｃ_１−Ｃ_８）アルキルを表し；各Ｒ^１３は（Ｃ_２−Ｃ_６）アルキレンオキシを表し；各ａ＝１〜１０；並びに、Ａは（Ｃ_５−Ｃ_１２）シクロアルキルを表す）
の１種以上のエポキシド含有化合物との反応生成物である、銅電気めっき浴中の銅とめっきされる基体とを接触させ；並びに、基体上に銅層を堆積させるのに充分な時間にわたって電流密度を適用する：ことを含む、基体上に銅を堆積する方法をさらに提供する。 The present invention comprises one or more nitrogen-containing compounds and formula (I) or (II):

(In the formula, Y ¹ and Y ² are independently selected from H and (C _1- C ₄ ) alkyl; Z is Ar, R ¹² OArOR ¹² , (R ¹³ O) _a Ar (OR ¹³ ) _a , Cy , R ¹² CyR ¹² or (R ¹³ O) _a Cy (OR ¹³ ) _a ; r = 1-4; Ar = (C _6- C ₁₈ ) aryl; Cy = (C _5- C ₁₂ ) cycloalkyl; each R ¹² represents (C _1- C ₈ ) alkyl; each R ¹³ represents (C _2- C ₆ ) alkyleneoxy; each a = 1-10; and A represents (C _5- C ₁₂ ) cycloalkyl. Represent)
Provided is a reaction product with one or more epoxide-containing compounds of.
The present invention is a copper electroplating bath containing a copper ion source, an electrolyte and a smoothing agent, wherein the smoothing agent is one or more nitrogen-containing compounds and formula (I) or (II):

(In the formula, Y ¹ and Y ² are independently selected from H and (C _1- C ₄ ) alkyl; Z is Ar, R ¹² OArOR ¹² , (R ¹³ O) _a Ar (OR ¹³ ) _a , Cy , R ¹² CyR ¹² or (R ¹³ O) _a Cy (OR ¹³ ) _a ; r = 1-4; Ar = (C _6- C ₁₈ ) aryl; Cy = (C _5- C ₁₂ ) cycloalkyl; each R ¹² represents (C _1- C ₈ ) alkyl; each R ¹³ represents (C _2- C ₆ ) alkyleneoxy; each a = 1-10; and A represents (C _5- C ₁₂ ) cycloalkyl. Represent)
Also provided are copper electroplating baths, which are reaction products with one or more epoxide-containing compounds of.
The present invention is a copper electroplating bath containing a copper ion source, an electrolyte and a smoothing agent, wherein the smoothing agent is one or more nitrogen-containing compounds and formula (I) or (II):

(In the formula, Y ¹ and Y ² are independently selected from H and (C _1- C ₄ ) alkyl; Z is Ar, R ¹² OArOR ¹² , (R ¹³ O) _a Ar (OR ¹³ ) _a , Cy , R ¹² CyR ¹² or (R ¹³ O) _a Cy (OR ¹³ ) _a ; r = 1-4; Ar = (C _6- C ₁₈ ) aryl; Cy = (C _5- C ₁₂ ) cycloalkyl; each R ¹² represents (C _1- C ₈ ) alkyl; each R ¹³ represents (C _2- C ₆ ) alkyleneoxy; each a = 1-10; and A represents (C _5- C ₁₂ ) cycloalkyl. Represent)
The copper in the copper electroplating bath, which is the reaction product of one or more epoxide-containing compounds of the above, is brought into contact with the substrate to be plated; and the current is long enough to deposit a copper layer on the substrate. Applying Density: Further provides a method of depositing copper on a substrate, including.

It has been surprisingly found that the present invention provides a copper layer with a substantially smooth surface across PCB substrates, even on substrates with very small features, and even on substrates with various feature sizes. Was done. The copper layer deposited according to this method significantly reduced nodule-like defects as compared to copper deposits from electroplating baths using conventional smoothing agents. Furthermore, the present invention effectively deposits copper in through holes and blind via holes, i.e., the copper plating bath of the present invention has good uniform electrodeposition.

As used throughout the specification, the following abbreviations shall have the following meanings, unless the context clearly indicates otherwise: A = ampere; A / dm ² = ampere / square decimeter; ° C = degrees Celsius; g = grams; mg = milligrams; L = liters; L / m = liters / minute; ppm = parts per million; μm = microns = micrometers; mm = millimeters; cm = centimeters; DI = Deionization; and mL = milliliter. Unless otherwise indicated, all quantities are weight percent and all ratios are molar ratios. All numerical ranges are comprehensive and can be combined arbitrarily unless it is clear that such numerical ranges are constrained to be 100% in total.

As used throughout this specification, "feature" refers to a shape on a substrate. "Aperture" refers to recessed features such as through holes and blinds. As used throughout this specification, the term "plating" refers to metal electroplating. "Deposition" and "plating" are used interchangeably throughout this specification. "Halide" refers to fluorides, chlorides, bromides and iodides. Similarly, "halo" refers to fluoro, chloro, bromo and iodine. The term "alkyl" includes linear, branched and cyclic alkyl. The "accelerator" refers to an organic additive that increases the plating rate of an electroplating bath. "Inhibitor" refers to an organic additive that suppresses the plating rate of metals during electroplating. "Smoothing agent" refers to an organic compound capable of providing a substantially smooth (or flat) metal layer. The terms "leveler" and "smoothing agent" are used interchangeably throughout this specification. The terms "printed circuit board" and "printed wiring board" are used interchangeably throughout this specification.

The plating baths and methods of the present invention are useful for providing a substantially smooth plated copper layer on a substrate such as a printed circuit board. The present invention is also useful for filling the aperture in the substrate with copper. Such filled apertures are substantially free of voids. Also, the copper deposits from the present invention are substantially free of nodules, i.e. copper deposits contain no less than 15 nodules / 95 cm ² surface area.

Any substrate in which copper can be electroplated onto the substrate is useful in the present invention. Such substrates include, but are not limited to, electronic devices such as printed wiring boards, integrated circuits, semiconductor packages, leadframes and internal connections. The substrate is preferably a PCB or an integrated circuit. In certain embodiments, the integrated circuit substrate is a wafer used in the dual damascene manufacturing process. Such substrates typically include a large number of features of various sizes, especially apertures. Through-holes in PCBs can have various diameters, eg, 50 μm to 150 μm. The depth of such through holes can be changed to 35 μm to 100 μm. PCBs can include blinds with various sizes, eg, 200 μm or less, or larger. The present invention is particularly suitable for filling apertures of various aspect ratios, such as low aspect ratio vias and high aspect ratio apertures. "Low aspect ratio" means an aspect ratio of 0.1: 1 to 4: 1. The term "high aspect ratio" refers to an aspect ratio greater than 4: 1, such as 10: 1 or 20: 1.

（式中、Ｙ^１およびＹ^２は独立してＨおよび（Ｃ_１−Ｃ_４）アルキルから選択され；ＺはＡｒ、Ｒ^１２ＯＡｒＯＲ^１２、（Ｒ^１３Ｏ）_ａＡｒ（ＯＲ^１３）_ａ、Ｃｙ、Ｒ^１２ＣｙＲ^１２もしくは（Ｒ^１３Ｏ）_ａＣｙ（ＯＲ^１３）_ａ；ｒ＝１〜４；Ａｒ＝（Ｃ_６−Ｃ_１８）アリール；Ｃｙ＝（Ｃ_５−Ｃ_１２）シクロアルキル；各Ｒ^１２は（Ｃ_１−Ｃ_８）アルキルを表し；各Ｒ^１３は（Ｃ_２−Ｃ_６）アルキレンオキシを表し；各ａ＝１〜１０；並びに、Ａは（Ｃ_５−Ｃ_１２）シクロアルキルを表す）
の１種以上のエポキシド含有化合物との反応生成物である。銅めっき浴は、典型的には、ハライドイオン源、促進剤および抑制剤も含む。 The copper plating bath of the present invention contains a copper ion source, an electrolyte and a smoothing agent, and the smoothing agent is combined with one or more nitrogen-containing compounds according to the formula (I) or (II):

(In the formula, Y ¹ and Y ² are independently selected from H and (C _1- C ₄ ) alkyl; Z is Ar, R ¹² OArOR ¹² , (R ¹³ O) _a Ar (OR ¹³ ) _a , Cy , R ¹² CyR ¹² or (R ¹³ O) _a Cy (OR ¹³ ) _a ; r = 1-4; Ar = (C _6- C ₁₈ ) aryl; Cy = (C _5- C ₁₂ ) cycloalkyl; each R ¹² represents (C _1- C ₈ ) alkyl; each R ¹³ represents (C _2- C ₆ ) alkyleneoxy; each a = 1-10; and A represents (C _5- C ₁₂ ) cycloalkyl. Represent)
It is a reaction product with one or more epoxide-containing compounds of. Copper plating baths typically also include a halide ion source, accelerators and inhibitors.

Any copper ion source that is at least partially soluble in the electroplating bath is suitable. Preferably, the copper ion source is soluble in the plating bath. Suitable copper ion sources are copper salts and, but are not limited to, copper sulfate; copper halides such as copper chloride; copper acetate; copper nitrate; copper borofluoride; copper alkylsulfonate; copper arylsulfonate; sulfamine. Copper acid; and copper gluconate. Typical copper alkyl sulfonates include (C _1- C ₆ ) copper alkyl sulfonates, more preferably (C _1- C ₃ ) copper alkyl sulfonates. Preferred copper alkyl sulfonates are copper methane sulfonate, copper ethane sulfonate and copper propane sulfonate. Typical copper aryl sulfonates include, but are not limited to, copper phenyl sulfonate, copper phenol sulfonate, and copper p-toluene sulfonate. Copper sulphate and copper methanesulfonate are preferred. A mixture of copper ion sources can be used. Those skilled in the art will appreciate that one or more salts of metal ions other than copper ions can be advantageously added to the present electroplating bath. The addition of such other metal ion sources is useful for the deposition of copper alloys. Such copper salts are generally commercially available and can be used without further purification.

The copper salt can be used in the main plating bath in an amount that provides sufficient copper ion concentration to electroplat the copper on the substrate. Preferably, the copper salt is present in an amount sufficient to provide an amount of 10-180 g / L of copper metal in the plating solution. Alloys such as copper-tin, for example copper having up to 2% by weight tin, can be advantageously plated according to the present invention. Other suitable copper alloys include, but are not limited to, copper-silver, tin-copper-silver, and tin-copper-bismuth. Each amount of metal salt in such a mixture will be determined depending on the specific alloy to be plated, and the amount will be well known to those of skill in the art.

Electrolytes useful in the present invention can be alkaline or acidic. Suitable acidic electrolytes include, but are not limited to, sulfuric acid, acetic acid, fluoroboric acid, alkane sulfonic acid, such as methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid and trifluoromethane sulfonic acid, aryl sulfonic acid, such as phenyl. Included are sulfonic acids, phenol sulfonic acids and toluene sulfonic acids, sulfamic acid, hydrochloric acid and phosphoric acid. A mixture of acids can be advantageously used in the present metal plating bath. Preferred acids include sulfuric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and mixtures thereof. The acid is preferably present in an amount in the range of 1-300 g / L, more preferably 5-250 g / L, even more preferably 10-225 g / L. Electrolytes are generally commercially available from a variety of sources and can be used without further purification.

Such electrolytes can optionally include a halide ion source. Chloride ion is the preferred halide ion. Typical chloride ion sources include copper chloride and hydrochloric acid. A wide range of halide ion concentrations can be used in the present invention. Typically, the halide ion concentration is in the range of 0 to 100 ppm, preferably 10 to 100 ppm with respect to the plating bath. The preferred amount of halide ion is 20-75 ppm. Such halide ion sources are generally commercially available and can be used without further purification.

The plating bath typically contains an accelerator. Any accelerator (also referred to as a brightener) is suitable for use in the present invention. Such accelerators are well known to those of skill in the art. A typical accelerator contains one or more sulfur atoms and has a molecular weight of 1000 or less. Accelerator compounds that have sulfide and / or sulfonic acid groups are generally preferred, particularly, formula: R'-S-R-SO 3 X ( wherein, optionally substituted alkyl, an optionally substituted R is Compounds containing a group of heteroalkyl, optionally substituted aryl or optionally substituted heterocyclic groups; X is a counterion, eg, sodium or potassium; and R'is a hydrogen or chemical bond) are preferred. .. Typically, the alkyl group is (C _1- C ₁₆ ) alkyl and preferably (C _3- C ₁₂ ) alkyl. Heteroalkyl groups typically have one or more heteroatoms, such as nitrogen, sulfur or oxygen, in the alkyl chain. Suitable aryl groups include, but are not limited to, phenyl, benzyl, biphenyl and naphthyl. Suitable heterocyclic groups typically include 1 to 3 heteroatoms, such as nitrogen, sulfur or oxygen, and include 1 to 3 separate or fused ring systems. Such heterocyclic groups can be aromatic or non-aromatic. Specific accelerators preferred for use in the present invention include, but are not limited to, N, N-dimethyl-dithiocarbamic acid- (3-sulfopropyl) ester; 3-mercapto-propylsulfonic acid- (3-sulfopropyl). ) Estel; 3-mercapto-propyl sulfonic acid sodium salt; 3-mercapto-1-propanesulfonic acid potassium salt and carbonate-dithio-o-ethyl ester-s-ester; bis-sulfopropyl disulfide; 3- (benzothiazolyl-) s-thio) sodium propyl sulfonic acid salt; pyridinium propyl sulfobetaine; 1-sodium-3-mercaptopropan-1-sulfonate; N, N-dimethyl-dithiocarbamic acid- (3-sulfoethyl) ester; 3-mercapto-ethylpropyl Sulfonic acid- (3-sulfoethyl) ester; 3-mercapto-ethyl sulfonic acid sodium salt; 3-mercapto-1-ethanesulfonic acid potassium salt and carbonate-dithio-o-ethyl ester-s-ester; bis-sulfoethyl Disulfide; 3- (benzothiazolyl-s-thio) ethyl sulfonic acid sodium salt; pyridinium ethyl sulfobetaine; and 1-sodium-3-mercaptoethane-1-sulfonate.

Such accelerators can be used in various amounts. Generally, the accelerator is used in an amount of at least 0.01 mg / L, preferably at least 0.5 mg / L, more preferably at least 1 mg / L relative to the bath. For example, the accelerator is present in an amount of 0.1 mg / L to 200 mg / L. The specific amount of accelerator will be determined according to the specific application such as high aspect ratio, through hole filling, and via filling applications. The preferred amount of accelerator useful in the present invention is at least 0.5 mg / L, more preferably at least 1 mg / L. The preferred range for such accelerator concentrations is 0.1-10 mg / L.

Any compound capable of suppressing the copper plating rate can be used as an inhibitor in the present electroplating bath. Suitable inhibitors include, but are not limited to, polymeric substances, particularly those with heteroatom substitutions, more preferably those with oxygen substitutions. Typical inhibitors high molecular weight polyether, for example, the _{formula: R-O- (CXYCX'Y'O) n} R '( wherein, R and R' are _{independently, H,} (C 2 _{-C 20} ) Alkyl group and (C _6- C ₁₀ ) aryl group; each of X, Y, X'and Y'is independently hydrogen, alkyl, eg methyl, ethyl or propyl, aryl, eg phenyl. , Or alalkyl, eg, benzyl; n is an integer of 3 to 10,000). Preferably, one or more of X, Y, X'and Y'is hydrogen. Preferred inhibitors include commercially available polypropylene glycol copolymers and polyethylene glycol copolymers such as ethylene oxide-propylene oxide (EO / PO) copolymers and butyl alcohol-ethylene oxide-propylene oxide copolymers. Suitable butyl alcohol-ethylene oxide-propylene oxide copolymers have a weight average molecular weight of 500 to 10,000, preferably 1000 to 10,000. When such inhibitors are used, the inhibitors are typically present in an amount in the range of 1 to 10,000 ppm, preferably 5 to 10,000 ppm based on the weight of the bath.

The reaction product of the present invention comprises at least one nitrogen-containing compound reacted with the epoxide-containing compound of formula (I) or (II). Such nitrogen-containing compounds can be acyclic or cyclic. Preferably, the nitrogen-containing compound is cyclic. More preferably, nitrogen is contained within such a cyclic group, i.e., a nitrogen-containing heterocyclic compound is more preferred than a nitrogen-containing compound. Suitable nitrogen-containing compounds include, but are not limited to, amines, amides, ureas, guanides, uracils, thiouracils, pyrrolidines, imidazoles, triazoles, tetrasols, benzimidazoles, benzotriazoles. , Piperidines, morpholins, piperazins, pyridines, oxazoles, benzoxazoles, pyrimidines, quinolines and isoquinolins. Such nitrogen-containing compounds can contain more than one nitrogen atom.

Suitable amines for use in the present invention include primary, secondary and tertiary amines. Preferably the amine compound is a secondary amine or a tertiary amine. Such amines can be monoamines, diamines, triamines and the like. Monoamines and diamines are preferred. Suitable amines can be acyclic or cyclic amines. Typical acyclic amines are of the formula: R ¹ R ² R ³ N (in the formula, R ¹ and R ² are independently H, (C _1- C ₆ ) alkyl, aryl (C _1- C _6). ) Alkyl, (C _1- C ₆ ) alkyl NR ⁴ R ⁵ and aryl; R ³ is selected from (C _1- C ₆ ) alkyl, aryl (C _1- C ₆ ) alkyl, and aryl; Also, R ⁴ and R ⁵ are independently selected from H and (C _1- C ₆ ) alkyl). Aryl groups may be substituted with one or more substituents such as halo, (C _1- C ₄ ) alkyl, (C _1- C ₄ ) alkoxy, and hydroxy. Suitable acyclic amine compounds useful for producing the present smoothing agent include, but are not limited to, di (C _1- C ₆ ) alkyl amines, tri (C _1- C ₆ ) alkyl amines, alkylene diamines, etc. Alkylated alkylenediamines, aryl (C _1- C ₆ ) alkyl amines, aryl di (C _1- C ₆ ) alkyl amines, and diaryl amines can be mentioned. Such acyclic amines include diethylamine, dipropylamine, dibutylamine, tripropylamine, ethylenediamine, N, N, N'N'-tetramethylethylenediamine, propylenediamine, cyclopentylamine, cyclopentylmethylamine, cyclohexylamine. , Cyclohexylmethylamine, cyclohexylbis (methylamine), aniline, N-methylaniline, N, N-dimethylaniline, diphenylamine, benzylamine and dibenzylamine.

Cyclic nitrogen-containing compounds suitable for producing the reaction product can be used. Typical types of cyclic amine compounds include, but are not limited to, pyrrolidines, imidazoles, triazoles, tetrazole, benzimidazoles, benzotriazoles, piperazines, morpholines, piperazines, pyridines, etc. Examples thereof include oxazoles, benzoxazoles, pyrimidines, quinolines and isoquinolins. It will be appreciated by those skilled in the art that each type of cyclic amine compound comprises an unsubstituted cyclic amine as well as a substituted cyclic amine. By way of example, the types of imidazoles include imidazoles themselves, and various substituted imidazoles. Substituent cyclic amines are those in which one or more hydrogen atoms are halo, cyano, (C _1- C ₄ ) alkyl, hydroxy (C _1- C ₄ ) alkyl, aryl and aryl (C _1- C ₄ ) alkyl. It means that it is replaced by one or more substituents such as. This aryl group may be substituted or unsubstituted. Typical substituents include, but are not limited to, methyl, ethyl, propyl, butyl, phenyl, trill, xsilyl, benzyl and phenethyl. Preferred types of cyclic amine compounds include imidazoles and pyridines. Preferred cyclic amine compounds include imidazole; 4-methylimidazole; 4-phenylimidazole; 5-phenylimidazole; 4,5-dimethylimidazole; 2-phenylimidazole; 2-methylimidazole; 2-butyl-4-hydroxymethyl. Imidazole; 4,5-dicyanoimidazole; 2-ethylimidazole; 4-ethylimidazole; 2-isopropylimidazole; 4-hydroxymethylimidazole; 4-hydroxyethylimidazole; 4,5-dichloroimidazole; 2- (naphthylmethyl) imidazole 2-Ethyl-4-methylimidazole; benzimidazole; 2-hydroxybenzimidazole; 2-methylbenzimidazole; pyridine; 2,6-pyridinedimethanol; 3-pyridinepropanol; 2-methylpyridine; 4-methylpyridine; Included are 2,4-dimethylpyridine; pyrrolidine, N-methylpyrrolidin, triazole; benzotriazole; and tetrazole.

Amine compounds useful in the present invention are generally commercially available from various sources such as Sigma-Aldrich (St. Louis, Missouri) or can be prepared by methods in the literature.

（式中、Ｙ^１およびＹ^２は独立してＨおよび（Ｃ_１−Ｃ_４）アルキルから選択され；ＺはＡｒ、Ｒ^１２ＯＡｒＯＲ^１２、（Ｒ^１３Ｏ）_ａＡｒ（ＯＲ^１３）_ａ、Ｃｙ、Ｒ^１２ＣｙＲ^１２もしくは（Ｒ^１３Ｏ）_ａＣｙ（ＯＲ^１３）_ａ；ｒ＝１〜４；Ａｒ＝（Ｃ_６−Ｃ_１８）アリール；Ｃｙ＝（Ｃ_５−Ｃ_１２）シクロアルキル；各Ｒ^１２は（Ｃ_１−Ｃ_８）アルキルを表し；各Ｒ^１３は（Ｃ_２−Ｃ_６）アルキレンオキシを表し；各ａ＝１〜１０；並びに、Ａは（Ｃ_５−Ｃ_１２）シクロアルキルを表す）
の化合物である。好ましくは、ＺはＡｒ、Ｒ^１２ＯＡｒＯＲ^１２、（Ｒ^１３Ｏ）_ａＡｒ（ＯＲ^１３）_ａ、もしくはＲ^１２ＣｙＲ^１２である。好ましくは、ｒ＝１〜３、より好ましくは１〜２である。各Ａｒ基は場合によっては、１以上の水素を置換基、例えば、これに限定されないが、（Ｃ_１−Ｃ_４）アルキル、（Ｃ_１−Ｃ_４）アルコキシおよびハロゲンで置き換えることによって置換されることができる。Ａｒは好ましくは（Ｃ_６−Ｃ_１５）アリールである。典型的なアリール基には、これに限定されないが、フェニル、メチルフェニル、ナフチル、ピリジニル、ビスフェニルメタン、および２，２−ビスフェニル−プロパンが挙げられる。Ｃｙは好ましくは（Ｃ_６−Ｃ_８）シクロアルキルである。Ａについての（Ｃ_５−Ｃ_１２）シクロアルキル基は、単環式、スピロ環式、縮合および／または二環式基であることができる。好ましくは、Ａは（Ｃ_８−Ｃ_１０）シクロアルキル、より好ましくはシクロオクチルである。各Ｒ^１２は好ましくは（Ｃ_１−Ｃ_６）アルキル、より好ましくは（Ｃ_１−Ｃ_４）アルキルである。各Ｒ^１３は好ましくは（Ｃ_２−Ｃ_４）アルキレンオキシである。ａ＝１〜８が好ましく、より好ましくは１〜６、さらにより好ましくは１〜４である。 The epoxide-containing compound used in this reaction product is of formula (I) or (II) :.

(In the formula, Y ¹ and Y ² are independently selected from H and (C _1- C ₄ ) alkyl; Z is Ar, R ¹² OArOR ¹² , (R ¹³ O) _a Ar (OR ¹³ ) _a , Cy , R ¹² CyR ¹² or (R ¹³ O) _a Cy (OR ¹³ ) _a ; r = 1-4; Ar = (C _6- C ₁₈ ) aryl; Cy = (C _5- C ₁₂ ) cycloalkyl; each R ¹² represents (C _1- C ₈ ) alkyl; each R ¹³ represents (C _2- C ₆ ) alkyleneoxy; each a = 1-10; and A represents (C _5- C ₁₂ ) cycloalkyl. Represent)
It is a compound of. Preferably, Z is Ar, R ¹² OArOR ¹² , (R ¹³ O) _a Ar (OR ¹³ ) _a , or R ¹² CyR ¹² . Preferably, r = 1-3, more preferably 1-2. Each Ar group is optionally substituted by substituting one or more hydrogens with substituents such as, but not limited to, (C _1- C ₄ ) alkyl, (C _1- C ₄ ) alkoxy and halogen. be able to. Ar is preferably (C _6- C ₁₅ ) aryl. Typical aryl groups include, but are not limited to, phenyl, methylphenyl, naphthyl, pyridinyl, bisphenylmethane, and 2,2-bisphenyl-propane. Cy is preferably _(C 6 -C ₈₎ cycloalkyl. The (C _5- C ₁₂ ) cycloalkyl group for A can be monocyclic, spirocyclic, condensed and / or bicyclic. Preferably, A is (C _8- C ₁₀ ) cycloalkyl, more preferably cyclooctyl. Each R ¹² is preferably (C _1- C ₆ ) alkyl, more preferably (C _1- C ₄ ) alkyl. Each R ¹³ is preferably (C _2- C ₄ ) alkyleneoxy. a = 1 to 8, more preferably 1 to 6, and even more preferably 1 to 4.

式中、Ｙ^１およびＹ^２は独立してＨおよび（Ｃ_１−Ｃ_４）アルキルから選択され；各Ｒ^６およびＲ^７は独立してＨ、ＣＨ_３およびＯＨから選択され；各Ｒ^１１は（Ｃ_１−Ｃ_４）アルキルもしくは（Ｃ_１−Ｃ_４）アルコキシを表し；ｂ＝０〜４；ｐ＝１〜６；並びにｑ＝０または１である。Ｙ^１およびＹ^２は好ましくは独立してＨおよび（Ｃ_１−Ｃ_２）アルキルから選択される。より好ましくは、Ｙ^１およびＹ^２は両方ともＨである。ｐ＝１〜４が好ましく、より好ましくは１〜３、さらにより好ましくは１〜２である。ｑ＝０の場合には環構造は５員炭素環式環であり、ｑ＝１の場合には環構造は６員炭素環式環である。式Ｉｄの典型的な化合物は、１，２−シクロヘキサンジメタノールジグリシジルエーテル、および１，４−シクロヘキサンジメタノールジグリシジルエーテル、および好ましくは１，４−シクロヘキサンジメタノールジグリシジルエーテルである。 Typical reaction products of formula (I) include, but are not limited to, compounds of formulas Ia, Ib, Ic and Id below:

In the formula, Y ¹ and Y ² are independently selected from H and (C _1- C ₄ ) alkyl; each R ⁶ and R ⁷ are independently selected from H, CH ₃ and OH; each R ¹¹ is Represents (C _1- C ₄ ) alkyl or (C _1- C ₄ ) alkoxy; b = 0-4; p = 1-6; and q = 0 or 1. Y ¹ and Y ² are preferably independently selected from H and (C _1- C ₂ ) alkyl. More preferably, both Y ¹ and Y ² are H. p = 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2. When q = 0, the ring structure is a 5-membered carbocyclic ring, and when q = 1, the ring structure is a 6-membered carbocyclic ring. Typical compounds of formula Id are 1,2-cyclohexanedimethanol diglycidyl ether, and 1,4-cyclohexanedimethanol diglycidyl ether, and preferably 1,4-cyclohexanedimethanol diglycidyl ether.

の化合物が挙げられる。式ＩＩの他の好ましい化合物には、ジシクロペンタジエンジオキシドおよび１，６−ジエポキシシクロデカンが挙げられる。 Typical reaction products of formula (II) are, but are not limited to, formula IIa:

Compounds include. Other preferred compounds of formula II include dicyclopentadiene dioxide and 1,6-diepoxycyclodecane.

Epoxide-containing compounds useful in the present invention can be obtained from a variety of commercially available sources, such as Sigma-Aldrich, or can be prepared using a variety of literature methods known in the art.

The reaction product of the present invention can be produced by reacting the above-mentioned one or more amine compounds with the above-mentioned one or more epoxide-containing compounds. Typically, the desired amount of imidazole and epoxy-containing compound is placed in the reaction flask, then water is added. The resulting mixture is heated at about 75-95 ° C. for 4-6 hours. After a further 6-12 hours of stirring at room temperature, the resulting reaction product is diluted with water. The reaction product can be used as is in aqueous solution, can be purified, or can be isolated if desired.

Generally, the reaction product has a number average molecular weight (Mn) of 500 to 10,000, but reaction products having other Mn values may be used. Such reaction products can have a weight average molecular weight (Mw) value in the range of 1000 to 50,000, but other Mw values may be used. Typically, Mw is 1000-20,000. In certain embodiments, Mw is 1500-5000. In another embodiment, Mw is 5,000 to 15,000.

Typically, the ratio of one or more amine compounds: one or more epoxide-containing compounds is 0.1: 10 to 10: 0.1. Preferably, this ratio is 0.5: 5-5: 0.5, more preferably 0.5: 1-1: 0.5. Other suitable ratios of amine compounds: epoxide-containing compounds may be used to produce the present smoothing agent.

It will be appreciated by those skilled in the art that the reaction products of the present invention may also have functionality capable of acting as inhibitors. Such compounds can be dual functional, i.e. they can function as smoothing agents and inhibitors.

The amount of reaction product (smoothing agent) used in the metal electroplating bath depends on the specific smoothing agent selected, the concentration of metal ions in the electroplating bath, the specific electrolyte used, and the electrolyte. It will depend on the concentration and the current density applied. Generally, the total amount of smoothing agent in the electroplating bath is 0.01 ppm to 5000 ppm based on the total weight of the plating bath, but more or less may be used. .. Preferably, the total amount of smoothing agent is 0.5-5000 ppm, more preferably 0.5-1000 ppm, even more preferably 0.5-100 ppm.

The smoothing agent of the present invention can have some suitable molecular weight polydispersity. The smoothing agent functions over various molecular weight polydispersity ranges.

The electroplating bath of the present invention is typically water-based. Unless otherwise specified, all concentrations of the component are in an aqueous system. Particularly suitable compositions useful as electroplating baths in the present invention include soluble copper salts, acid electrolytes, accelerators, inhibitors, halide ions, and the reaction products described above as smoothing agents. More preferably, suitable compositions include a soluble copper salt of 10 to 220 g / L as a copper metal, an acid electrolyte of 5 to 250 g / L, an accelerator of 1 to 50 mg / L, an inhibitor of 1 to 10,000 ppm. It contains 10 to 100 ppm of halide ions and 0.25 to 5000 ppm of the reaction product described above as a smoothing agent.

The electroplating bath of the present invention can be produced by combining the components in any order. Inorganic components such as copper ion sources, water, electrolytes, and any halide ion source are first placed in the bath vessel, then organic components such as smoothing agents, accelerators, inhibitors and some other organic components. Is added.

The electroplating bath may optionally contain a second smoothing agent. This second smoothing agent can be another smoothing agent of the present invention, or it can be some conventional smoothing agent. Suitable conventional smoothing agents that can be used in combination with this smoothing agent are, but are not limited to, US Pat. Nos. 6,610,192 (Step et al.), 7,128,822 (Wan et al.), Examples include those disclosed in Nos. 7,374,652 (Hayashi et al.) And 6,800,188 (Hagiwara et al.). Such a combination of smoothing agents can be used to adjust the characteristics of the plating bath, including smoothing ability, uniform electrodeposition and nodule reduction.

The plating bath of the present invention can be used at a temperature of 10 to 65 ° C. or higher. Preferably, the temperature of the plating bath is 10 to 35 ° C, more preferably 15 to 30 ° C.

Generally, the copper electroplating bath is agitated during use. Any suitable stirring method can be used for the present invention, such methods are well known in the art. Suitable agitation methods include, but are not limited to, air sparging, workpiece agitation, and collision.

Typically, the substrate is electroplated by contacting the substrate with the plating bath of the present invention. The substrate typically functions as a cathode. The plating bath houses the anode, which can be soluble or insoluble. The potential is typically applied to the cathode. Sufficient current densities are applied and plating is performed over a period of time sufficient to deposit a copper layer of the desired thickness on the substrate and to fill the blinds and / or through holes. Suitable current densities include, but are not limited to, the range of 0.05-10 A / dm ² , but higher and lower current densities may be used. The specific current density is determined in part depending on the substrate to be plated and the smoothing agent selected. The choice of such current density is within the capacity of those skilled in the art.

The present invention is useful for depositing copper layers on various substrates, especially those with apertures of various sizes. Thus, the present invention comprises contacting a copper-plated substrate with the copper plating bath described above; and then applying a current density over a time sufficient to deposit a copper layer on the substrate. , Provide a method of depositing a copper layer on a substrate. For example, the present invention is particularly suitable for depositing copper on printed circuit boards with blinds and through holes.

According to the present invention, copper is deposited in the aperture without substantially forming voids in the metal deposit. The term "without substantially forming voids" means that more than 95% of the plated apertures are void-free. It is preferable that the plated aperture contains no voids. Copper is also uniformly deposited in through-holes and in high-aspect ratio through-holes with improved uniform electrodeposition, surface distribution and thermal reliability.

Although the methods of the invention have generally been described in connection with the production of printed circuit boards, for any electrolytic process in which an essentially smooth or flat copper deposit and a virtually free of void-filled aperture are desired. , It will be recognized that the present invention may be useful. Such processes include semiconductor packaging and interconnect manufacturing.

The advantage of the present invention is that a substantially smooth copper deposit is obtained on the PCB. A "substantially smooth" copper layer is a step height, i.e., a difference of 5 μm between a region with densely packed very small apertures and a region with or without apertures. It means that it is less than, preferably less than 1 μm. Through holes and / or blinds in the PCB are substantially filled with virtually no voiding. In addition, such copper deposits reduced nodule formation compared to conventional copper plating processes. A further advantage of the present invention is that a wide range of apertures and aperture sizes can be packed within a single substrate without substantially suppressing partial plating. Therefore, the present invention is particularly suitable for filling blinds and / or through-holes in printed circuit boards, such planed advisors and through-holes having substantially no additional defects. "Substantially free of additional defects" means that the smoothing agent compares the number or size of void-like defects in the filling aperture with a control plating bath that does not contain such a smoothing agent. It means not to increase. A further advantage of the present invention is that a substantially flat copper layer can be deposited on a PCB with non-uniformly sized apertures. "Aperture of non-uniform size" refers to apertures of various sizes in the same PCB.

Uniform electrodeposition is defined as the ratio of the average thickness of the metal plated in the center of the through hole to the average thickness of the metal plated on the surface of the PCB sample and is reported as a percentage. The higher the uniform electrodeposition, the better the plating bath can fill the through holes. The copper plating bath of the present invention has a uniform electrodeposition property of 70% or more, preferably 75% or more, more preferably 80% or more. The copper-plated bath of the present invention also exhibits reduced nodule formation on copper-plated substrates as compared to conventional copper-plated baths. Preferably, the copper plating bath provides a copper deposit having 15 nodules or less / 95 cm ² surface area, more preferably 10 nodules or less / 95 cm ² , and even more preferably 8 nodules or less / 95 cm ² . Uniform electrodeposition, the amount of nodules formed and the cracking percentage are all determined as described in Example 7.

Example 1
Resorcinol diglycidyl ether (94.5 mmol), 150 mmol imidazole and 10 mL diethylene glycol were placed in a round bottom reaction flask set in a heating bath at room temperature. 40 mL of DI water was then added to the flask. The temperature of the heating bath was set to 98 ° C. The initially formed white suspension gradually dissolved as the reaction temperature increased, resulting in a clear amber solution. The reaction mixture was heated for 5 hours and stirred at room temperature for an additional 8 hours. This reaction product (reaction product 1) was used without further purification. Feature data for this reaction product is shown in Table 1 below. The actual stock solution of this product was prepared using water as the solvent.

Example 2
2,4-Dimethylimidazole (100 mmol), 56.7 mmol of 1,4-butanediol diglycidyl ether and 6.3 mL of resorcinol diglycidyl ether were placed in a round bottom reaction flask set in a heating bath at room temperature. .. Then 15 mL of DI water was added to the flask. The temperature of the heating bath was set to 95 ° C. The reaction mixture was heated for 6 hours and stirred at room temperature for an additional 8 hours. This reaction product formation (amber) (reaction product 9) was used without further purification. Feature data for this reaction product is shown in Table 1 below. The actual stock solution of this product was prepared using DI water as the solvent.

Example 3
Reaction products 2-8 were produced according to the procedure of Example 1 or 2. The molar ratios of the components and the characteristic data of the reaction products are shown in Table 1. UV-absorption of the reaction product is measured in water using an Agilent 8453 spectrophotometer, and λ _max (nm) is reported in the table below.

Example 4
The reaction products in Table 2 are expected to be produced according to the procedure of Example 1 or 2. The following abbreviations are used in Table 2: t-Bu = tertiary butyl; Pr = propyl; Me = methyl; Et = ethyl; and Ph = phenyl.

Example 5
Using imidazole as an amine compound and epichlorohydrin as an epoxy-containing compound in a molar ratio of 1: 2, the comparative reaction product C-, which is a conventional smoothing agent, generally follows the procedure of Example 1. 1 was manufactured.

Example 6
Various copper plating by combining 75 g / L copper (as copper sulphate pentahydrate), 240 g / L sulfuric acid, 60 ppm chloride ion, 1-3 ppm accelerator and 1.5 g / L inhibitor The bath was manufactured. The accelerator was a disulfide compound with a sulfonic acid group and a molecular weight of less than 1000. The inhibitor was an EO / PO copolymer having a molecular weight of less than 5,000 and one terminal ether group. Each plating bath also contained reaction products from Examples 1, 2, 3 or 5 in amounts as reported in Table 3. The specific amounts of accelerator (ACC.) Used in each plating bath are also reported in Table 3.

Example 7
A sample (either 3.2 mm or 1.6 mm thick) of a double-sided FR4 PCB (5 x 9.5 cm) with through holes was plated in a hurling cell using a copper plating bath according to Example 6. .. The 3.2 mm thick sample had a through hole with a diameter of 0.3 mm, and the 1.6 mm thick sample had a through hole with a diameter of 0.25 mm. The temperature of each bath was 25 ° C. A current density of 2.16 A / dm ² (20 A / ft ² ) or 3.24 A / dm ² (30 A / ft ² ) was applied to each bath over 80 minutes. Copper-plated samples were analyzed to determine the uniform electrodeposition (TP), nodule formation, and cracking percentage of the plating bath according to the following methods. The results are reported in Table 3.

Uniform electrodeposition is calculated by determining the ratio of the average thickness of the metal plated in the center of the through hole to the average thickness of the plated metal on the surface of the PCB sample and is reported as a percentage in Table 3. ..

Nodule formation was determined by visual inspection and by using the Reddington Tactile Test (RTT). Visual inspection showed the presence of nodules, while RTT was used to determine the number of nodules. The RTT used a human finger to sense the number of nodules in a given area of the plated surface, which in this example was both sides of the PCB sample (total area 95 cm ² ). ..

IPC-TM-650-2.6.8 Thermal Stress, Plated-Through Holes IPC (Northbrook, Illinois, USA), a standard procedure in the industry, published in 2004. In May of the year, the amount of cracking (reported as a percentage in Table 3) was determined according to revision E.

As can be seen from the data, the smoothing agents of the present invention significantly reduce nodule formation and also exhibit very good uniform electrodeposition as compared to conventional smoothing agents (C-1). ..

Claims (7)

Copper ion source ;
Electrolytes ;
Addition reaction generation of one or more nitrogen-containing compounds as smoothing agents, one or more epoxide-containing compounds of formula (Ia), (Id) or (II) and optionally epoxide-containing compounds of formula (Io). It ’s a thing,

(In the formula, Y ¹ and Y ² are independently selected from H and (C _1- C ₄ ) alkyl; each R ⁶ and R ⁷ are independently selected from H, CH ₃ and OH; each R ¹¹ Represents (C _1- C ₄ ) alkyl or (C _1- C ₄ ) alkoxy; b = 0-4; p = 1-6; and q = 0 or 1; and A is (C ₅ − C ₁₂ ) Represents cycloalkyl)
The nitrogen-containing compound is imidazole; 2-phenylimidazole; 2-methylimidazole; 4,5-dicyanoimidazole; 2-ethylimidazole; 2-isopropylimidazole; 4,5-dichloroimidazole; 2- (naphthylmethyl) imidazole; benz. It is selected from imidazole; pyridine; 2,6-pyridinedimethanol; 3-pyridinepropanol; 2-methylpyridine; 4-methylpyridine; 2,4-dimethylpyridine; triazole; benzotriazole; and tetrazole, wherein the 4, 5-Dicyanoimidazole, 4,5-dichloroimidazole, pyridine, 2,6-pyridinedimethanol, 3-pyridinepropanol, 2-methylpyridine, 4-methylpyridine, 2,4-dimethylpyridine, triazole, benzotriazole and tetrazole one or more hydrogen atoms on the ring of the selected halo, _{cyano, (C} 1 -C ₄₎ alkyl, hydroxy _(C 1 -C ₄₎ alkyl, aryl and aryl _(C 1 -C ₄₎ group consisting of alkyl Addition reaction product, which may be replaced by one or more substituents .
Copper electroplating bath containing. Copper ion source;
Electrolytes;
Addition reaction generation of one or more nitrogen-containing compounds as smoothing agents, one or more epoxide-containing compounds of formula (Ia), (Id) or (II) and optionally epoxide-containing compounds of formula (Io). It ’s a thing,

(In the formula, Y ¹ And Y ² Independently H and (C ₁ -C ₄ ) Selected from alkyl; each R ⁶ And R ⁷ H, CH independently ₃ And OH; each R ¹¹ Is (C ₁ -C ₄ ) Alkyl or (C ₁ -C ₄ ) Alkoxy; b = 0-4; p = 1-6; and q = 0 or 1; and A is (C) ₅ -C ₁₂ ) Represents cycloalkyl)
The nitrogen-containing compound is imidazole; 2-phenylimidazole; 2-methylimidazole; 4,5-dicyanoimidazole; 2-ethylimidazole; 2-isopropylimidazole; 4,5-dichloroimidazole; 2- (naphthylmethyl) imidazole; benz. Addition reaction product, selected from imidazole; pyridine; 2,6-pyridinedimethanol; 3-pyridinepropanol; 2-methylpyridine; 4-methylpyridine; 2,4-dimethylpyridine; triazole; benzotriazole; and tetrazole.
Copper electroplating bath including. The copper electroplating bath according to claim 1 or 2 , wherein the addition reaction product has a number average molecular weight of 500 to 10,000. The copper electroplating bath according to any one of claims 1 to 3 , further comprising a second smoothing agent. The copper electroplating bath according to any one of claims 1 to 4 is brought into contact with the substrate to be plated; and the current density is applied for a time sufficient to deposit a copper layer on the substrate; A method of depositing copper on a substrate, including. The method according to claim 5 , wherein the substrate is a printed circuit board. The method according to claim 6 , wherein the printed circuit board includes through holes.